Embodiments described herein relate generally to an ultrasound diagnostic apparatus and a biomedical examination apparatus.
Breast cancer is one of the causes of women death. Breast cancer screening and early diagnosis have very high values in terms of reducing mortality rate and suppressing the cost of health care.
Existing methods include palpation of breast tissues and X ray imaging for searching for suspected tissue deformation. If there is a suspected portion in an X ray photograph, ultrasound imaging is performed, and surgical tissue examination is further performed. A series of these examinations require much time to reach a final conclusion. In addition, since premenopausal young women have many mammary glands, high sensitivity is difficult to obtain in X ray imaging. Therefore, screening using ultrasound imaging has great significance for the young generation, in particular.
In general, in ultrasound imaging, a certified operator acquires ultrasound images, and an expert interpreter (a plurality of interpreters in some cases) makes determination from morphological information on the images. When performing medical examination, the maximum number of persons subjected to screening per operator per day is 50 in consideration of the risk of oversights caused by the fatigue and lack of concentration of the operator.
In order to acquire a still image capturing a morphological characteristic in ultrasound imaging, it is very important for the operator to have knowledge and experience. High skill is also required to perform accurate and quick screening. For example, standard examination times per object are 5 to 10 min. However, it sometimes takes more time for screening depending on the skill of an operator. That is, in screening based on current ultrasound imaging, the accuracy of image acquisition may vary depending on the levels of skill of operators. When acquiring images, the operator needs to keep paying close attention to images. Besides, he/she takes charge of making determination by himself/herself, and hence a heavy mental strain is imposed on him/her even if he/she is a skilled operator. Although there is available a scheme of acquiring all image information from a moving image, there is no established technique for automatic search using image recognition. For this reason, an interpreter searches a moving image for still images. In this case, a heavy burden is imposed on the interpreter.
In order to solve the above problem, the present applicant has proposed an apparatus with the concept of complement of ultrasound echo diagnosis by using a compact optical examination system designed to reduce a burden on a technician by guiding the measurement position of an ultrasound echo probe in a plane direction based on the metabolic information of the living body which is obtained by optical measurement. FIG. 18 shows the light absorption spectra of oxygenated hemoglobin and deoxygenated hemoglobin. In general, deoxygenated hemoglobin ratio in a malignant tumor region is higher in ratio than in a healthy region, and hence an analysis result on the absorption of deoxygenated hemoglobin is one of the bases for determining the degree malignancy of a target region in optical biomedical examination. The wavelength regions of light suitable for the light absorption measurement of deoxygenated hemoglobin are 740 nm to 790 nm in the near infrared light region and 650 nm to 690 nm in the red light region. The wavelength region of light suitable for the light absorption measurement of oxygenated hemoglobin is 830 nm to 900 nm in the near infrared light region. The wavelength region of light to identify a total hemoglobin amount is, for example, 800 nm to 820 nm in the near infrared light region. Specific light sources include an LED and an LD. In consideration of absorption wavelength of other biological components such as water, fat, and melanin and biodistributions, an output light intensity and a half width must be properly selected for a light source.
As a method of effectively detecting a suspected position in a breast cancer detection technique, there has also been proposed a method using a plurality of light sources having peaks at different wavelengths corresponding to the light absorption of oxygenated hemoglobin and deoxygenated hemoglobin. This method detects abnormal absorption based on a value (light intensity ratio) obtained by normalizing the light intensity of one light source with the light intensity of the other light source. In a normal region of the breast, since there is no difference in oxygen saturation in blood, normalized light intensities are almost constant. In contrast to this, a malignant tumor region such as a breast cancer region is higher in blood density and lower in oxygen saturation than the surrounding region, and hence it is possible to detect a difference in normalized light intensity. Detecting a normalized light intensity difference makes it possible to implement navigation to a suspected position (the position of an abnormal region or suspected abnormal region) or feedback to a precise measurement position at the time of automatic measurement.
As described above, normalized light intensities are effective for the navigation of a probe to a suspected position. On the other hand, in order to derive a light absorption coefficient in each region, it is necessary to perform analysis of each wavelength. When, for example, quantifying the oxygen saturation of a suspected cancer region, it is necessary to perform analysis to derive light absorption coefficients with respect to near-infrared wavelengths corresponding to oxygenated hemoglobin and deoxygenated hemoglobin. For this reason, normalized light intensities cannot be used for the quantification of oxygen saturations.
On the other hand, a serious problem in the actual measurement of the living body is a shift/variation in measurement light intensity caused by pressing and relaxing of a probe. The present inventors have solved this problem by performing the correction processing of performing normalization with a reference light source of a wavelength near to a measurement wavelength.
In general, however, the light intensity ratio difference between a healthy region and a suspected region is small. For this reason, using light intensity ratios sometimes makes it impossible to perform satisfactory appearance determination concerning a suspected region, and hence further improvements are demanded.
It is an object of an embodiment to provide an ultrasound diagnostic apparatus and living body examination apparatus which can accurately guide an optical ultrasound probe to a body surface portion corresponding to a suspected region when measuring light intensities by bringing the optical ultrasound probe into contact with the object.